Build 139 — December 2013/January 2014 — 35Build 149 — August/September 2015 — 35

DESIGNRIGHT

Poorly restrained or unrestrained building services can cause havoc during earthquakes, leaving buildings unusable afterwards. Prevent this by following the guidance on properly restraining building services.

BY ALIDE ELKINK, FREELANCE TECHNICAL WRITER, WELLINGTON

Seismic restraint of building services

RECENT EARTHQUAKES have highlighted the

potentially devastating consequences of

inadequately restrained building services such as

water reticulation, electricity supply, communi-

cations, heating, ventilation and air conditioning

(HVAC) and fire sprinkler systems.

Flooding may result from ruptured pipework,

a fire may break out due to electrical equipment

shorting and components may collapse onto

people causing injury or block exit routes. The

damage is likely to cause ongoing lost productivity.

Seismic restraint is mandatoryThe New Zealand Building Code clause B1

Structure requires that both structural and

non-structural building elements remain stable

under imposed loads such as those caused by

earthquakes.

It cites NZS 4219:2009 Seismic performance

of engineering systems in buildings, which sets

out design options for the seismic restraint

of non-structural engineering systems. These

are defined as permanently installed systems

to provide water, gas, steam, electrical and

communications services, environmental

control and active fire-fighting or fire-

suppression systems in a building.

Some building elements left outNZS 4219:2009 doesn’t cover some building ele-

ments, such as lifts, fire sprinklers and suspended

ceiling systems.

For these, the design should be in accordance

with two standards taken together – NZS

1170.5:2004 Structural design actions – Part 5:

Earthquake actions – New Zealand and either:

NZS 4219:2009 TABLE 15 – CLEARANCESTable 1

CONDITION BEING CONSIDERED MINIMUM CLEARANCE (MM)

HORIZONTAL VERTICAL

Unrestrained component to unrestrained component 250 50

Unrestrained component to restrained component 150 50

Restrained component to restrained component 50 50

Penetration through structure (such as walls and floors) 50 50

Note – Ceiling hangers and braces are considered to be restrained components for the purposes of this table.

Provided by Standards New Zealand under licence 001157.

● the appropriate materials standard (such as

NZS 3404:1997 Steel structures standard) or

● a specific system standard (such as AS/NZS

2785:2000 Suspended ceilings – Design and

installation for suspended ceilings).

Good seismic design principlesGood seismic design of engineering systems

includes incorporation of:

● fixings to provide seismic restraint

● adequate clearances

● flexible connections.

Fixings to restrain

Fixings should provide restraint and transfer

seismic loads to the building structure through

a continuous load path that matches or exceeds

the earthquake load demand of the building.

They include bolts, welds, anchors, brackets,

cleats and gusset plates that connect compon-

ents to each other, to the elements of a restraint

system and to the supporting structure.

Adequate clearances

NZS 4219:2009 Table 15 sets out minimum clear-

ances between building services and adjacent

components based on whether the respective

components are restrained or unrestrained.

Flexible connections

Flexible connections allow independent movement

under seismic displacement. They should be used:

● at seismic joints between adjacent buildings

● at seismic joints in base-isolated buildings.

For example, flexible connections should be used

to connect pipes to anchored equipment.

Vertical pipes should have enough flexibility to

accommodate the relative horizontal movement

between floors or fixing locations.

GUIDANCE IN THE BUILDING CODE AND STANDARDS FOR THE RESTRAINT OF BUILDING SERVICES

36 — Build 139 — December 2013/January 201436 — August/September 2015 — Build 149

Some restraints non-specific designGenerally seismic design is required to be

project-specific, which means the design must be

considered specifically for every different building

and engineering system.

However, NZS 4219:2009 allows ducting and

piping system restraints to be designed using a

non-specific design pathway if the installation

meets the criteria in the standard. This means

that, for some commonly used components,

it is possible to develop non-project-specific

solutions and adapt them for a specific

project. Solutions must be verified by a seismic

specialist.

Typical details where NZS 4219:2009 allows

non-specific design include:

● light fittings

● fan coil unit bracings details

● cable tray bracing

● duct bracing.

When conduit, cables and cable trays cross a

structural separation or seismic gap, they must be

specifically designed.

Suspended ceilingsMany suspended ceiling systems were damaged

during the Christchurch earthquakes. Problems

included dislodged and broken ceiling tiles,

failed grid connections and perimeter angles and

impact damage between ceiling components and

adjacent services.

AS/NZS 2785:2000 provides specific and

non-specific design pathways for suspended

ceilings. Non-specific design guidance is usually

provided by suspended ceiling manufacturers

with prescriptive solutions for particular ceiling

systems. Where ceilings are more complex,

specific design is required.

A proposed code of practice for design,

installation and seismic restraint of suspended

ceilings is being developed by the Association of

Wall and Ceiling Industries of New Zealand. They

expect to release it later in 2015.

Use a seismic specialist Seismic design is an integral part of building

design. It requires an integrated design and

coordination between building designers,

structural engineers and building services

engineers from the earliest stages of the building

project.

The design of non-structural systems such

as building services should be carried out or

supervised by a suitably qualified, competent

seismic design professional who can undertake

the design, inspection and sign-off for each

component. For more See the soon to be released BRANZ

seismic resilience resource at www.

seismicresilience.org.nz.

Seismic upgrade of University of Auckland Political Studies Building

Planitop HDM MaxiThe solution for structural reinforcement and seismic upgrades

Planitop HDM Maxi is a two-component, high-strength fibre-reinforced mortar for smoothing and levelling concrete and masonry.

• Planitop HDM Maxi may also be used on its own to repair andrestore the texture of masonry, or to level and even out the surfaceof reinforced concrete and masonry structures.

• Used in combination with Mapegrid G 220 mesh, Planitop HDMMaxi is used to consolidate structures, for structural reinforcingand increasing the shear/tensile strength of structures, especially inseismic zones.

• Planitop HDM Maxi has high adhesion strength and hardens toform a compact layer which is impermeable to water and aggressivegases while remaining permeable to water vapour.

www.mapei.co.nz

FRG System: Application of Planitop HDM Maxi and Mapegrid G 220 mesh on brick